Elizabeth f



3 Sheets-Sheet 2.

(No Model.)

` J. COIPIN, Deod.

E. F. GoFF1N,Exeutrix. PROGESS 0F TOUGHENING STEEL.

Patented May 12, 1891.

rm; imams refans un., mormmno., wAsHmcrruu, n. c.

, (No Model.) 3 Sheets-Sheet 3.

J. COFFIN, Decd.

E. F. COFFIN, Executrx. PROCESS 0E TOUGHENING STEEL.

No. 452,031. Patented May l2, 1891.

UNITED Terres' FFICE@ JOHN OOFFIN, OF JOHNSTOVN, PENNSYLVANIA; ELIZABETH F. OOFFIN (EXEOUTRIX OF SAID JOHN OOFFIN, DEOEASED) ASSIGNOR TO THE OAMBRIA IRON COMPANY.

PROCESS OF TOUGH ENING STEEL.

SPECIFICATION forming part of Letters Patent No. 452,031, dated May 12, 1891.

Application filed September 10, 1888. Serial No. 284:998. (No model.)

ToA @ZZ whom t may concern.-

Be it known that I, JOHN CoFnrN, a citizen of the United States, residing at Johnstown, in the county of Cambria and State of Pennsylvania, haw-einvented certain new and useful Improvements in Processes of Toughenin g Articles of Steel; and I d0 hereby declare the following to be a full, clear, and exact description of the invention, suoli as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to a method of toughening forged or cast articles ofsteel by subj ecting them to proper temperatures in a manner which will be set forth.

The object of my invention is to correct an improper structural arrangement of the component molecules of masses of steel and attain the maximum toughness and ductility in the said masses of steel. To accomplish this object I place the articles to be toughened in a suitable furnace and heat them to a certain temperature, which has before been termed XV, andI will use the terminology. This is the temperature at which the carbon has been supposed to change its chemical relation tol phous condition which is attained by heating toWV, it is 'necessary to cool quite rapidly through a certain range of temperature ex-V tending from XV to V. I will dene W as a temperature showing a low orange color in the dark, and V as a temperature showing a clear red in the dark. Heretofore when rapid cooling to temperature V has been resorted to to toughen articles of steel this coolinghas been performed in some liquid cooling medium; but in many cases the shape or size of the article to be treated is such that it is impossible to resort to this method of treatmentin the first place, on account of the-difficulty of handling rapidly enough a large piece of hot steel, and, in the second place, the danger of cracking or causing excessive strains in a piece of irregular section. Therefore in operating my present invention, after the articles of steel have been heated to temperature IV, I expose them to the rapid-cooling action of cold-air currents directed against and around them. After temperature V is reached by this means I discontinue the aircurrents and close the furnace up tightly and let the steel articles cool slowly until entirely cold. In some cases, where it is not thought best to use the air-currents, I remove the articles bodily from the furnace and let them cool in the open air from temperature XV to V, When I place them in the furnace again and seal the furnace up.

The furnace whichI use to carry my invention into effect is of novel construction, and consists in a roof, an end wall, and two side walls, all of which are stationary. The bottom and one end wall are contained on a strong truck which rolls on a lpermanent tramway. The bottom and one end can thus be bodily moved out from the main part of Vthe furnace, carrying with it the burden of steel articles Linder treatment. The principal use of this construction is to charge and discharge the furnace easily; but sometimes, where the pieces to be toughened are large and ofapeculiarshapefittedtoit,Iopen thefurnace in the before-described manner7 to cool the Steel from Wto V. Iuse the term open the furnace in this connection. It is really drawing the bottom out of the furnace.- Located in side walls of the furnace are suitable openings for gas-dames by which the furnace is heated. The products of combustion are carried away,'rst, through a pendent iiue located in thefbottom of the furnace, which registers, when "the furnace is closed, With a corresponding vertical flue built in the ground. This com municates with an underground horizontal flue, which in turn connects With a draft-stack located some suitable distance from the furnace. The object of having the flue pendent from the bottom is that by thus taking the product of combustion outof the furnace a more uniform distribution of heat is obtained. Located above the flame-openings are large ports, which, when the furnace is being heated, are closed with bricks. Located on the roof of the furnace are short large stacks, the interior openiu gs connecting directly to the interior of the furnace. Vhen the furnace is being heated, these stacks are closed by iron plates. After the furnace, with its contents, has come tothe proper temperature (YV) the gas is shut off, the plates removed from the tops of the short stacks, and the ports in the side opened, when drafts of cold air through the furnace areimmediately started. After the furnace, with its contents, is cooled down a sufficient amount the side ports are closed with brick, the iron plates are put on the short cooling-stacks, and all erevices securely stopped with clay. The furnace, with its contents, is then left in this condition until cold.

To make my description more clear, I will now refer to the annexed three sheets of drawings, which form part of this specification, and in which- Figure l represents a longitudinal section of the furnace on the center line of its plan; Fig. 2, a transverse sectional elevation on line X Y of Fig. l; Fig. 3, a horizontal section on line S T U R of Fig. 2, and Fig. 4 a scale on which these drawings are made.

Like letters of reference refer to like parts throughout.

The drawings accompanying this specification are made from working-drawings of a furnace now in use at the Cambria Iron Companys Vorks, at Johnstown, Pennsylvania. This furnace has been in successful operation for over a year, and has a capacity of about fifty thousand pounds of ordinary steel castings and forgings. The largest single piece toughened in it was a steel casting weighing forty thousand pounds.

AA represent the side wall, and A the stationary end wall, of the furnace; B, the roof C, the bottom, and D the movable end wall. The bottom is supported by a strong steel frame-work, consisting in the longitudinal I-beams c', to which are riveted the transverse girders c2 c2 c2 e2. This girder-frame supports a series of T-irons, one of which is designated by e3. Supported on top of the T-irons are cast-iron plates c4. The object of this is to create an air-space around the T- irons, so that they will be uniformly heated from the warmth of the bottom and maintain their straight position. Upon the plates c4 is laid the bottom c5, consistingof refractory brick.

c is the pendent vertical flue attached to the bottom, the construction of which is clearly indicated by the drawings. The girder framework, which has been described, forms part v of a truck, cG being the axles and c7 the wheels, which are double dan ged. The end wall D rests on the bottom truck and is braced in position by eye-bars d.

E is the tramway, which consists ofthe rails e and the iron cross-ties e.

F indicates the openings for the gas-llames, and fthe gas-nozzles. The openings F are of a size in such ratio to the size of the gasnozzles and pressure of the gas that a suitable amount of airV will be drawn in by the force of the gas-jet to give proper combustion. c

G represents the cooling-ports, and Il the cooling-stacks.

h is the plates which normally cover the cooling-fines.

K represents the vertical smoke-flue, and L the longitudinal passage. In operating the furnace after it is closed the crevice between pendent flue c and the flue 7c is filled with clay. The horizontal Hue L extends to a suitable draft-stack.

f represents the main gas-pipes, and f2 the cocks, which are placed on each separate nozzle.

The arrangement of buck-staves and tierods is evident from the drawings, and no further description is deemed necessary of these. i

The mode of operation is as follows: The truck carrying the bottom and end WallD is rolled out of the furnace, and the charge of steel articles it is design ed to treat is placed upon the bottom. The truck, with its burden, is now rolled in to its closed position, (shown clearly in Fig. 1,) the crevice at the bottom of the pendent flue is sealed up with clay, andthe several gas-jets are lighted. After about twenty-four hours, when the furnace, with its contents, has reached temperature WV, the gas is extinguished, the ports Gr opened, and the cover-plates h removed from the stacks H, when the circulating-currents of cold air rapidly cool the charge until temperature Vis reached, when the cover-,plates h are placed in position, the ports G bricked up, and all crevices stopped with clay. The whole is then allowed to stand until cold enough to handle, which generally takes about fortyeight hours, after which the truck carrying the end and bottom with its burden is rolled out and the charge removed.

I am aware that articles of steel have been rannealed by heating them to a proper temperature and allowing them to cool slowly. rlhis process has been practiced for many years. I am also aware that steel articles have been annealed by cooling in the open air. I am also aware that steel articles have been toughened by heating them to a proper temperature and then rapidly cooling through a certain range of temperature byimmersion in water, oil, or other liquid cooling medium, after which they have been allowed to cool slowly in the open air; but I am not aware that steel articles have everbeen toughened by heating to a proper temperature and cooling rapidly as possible in air through a certain IOC IIO

IIS

range of temperature and then finally in a sealed furnace.

Havingfullydescribed my invention and the manner of Working the same, and having 5 set forth the state of the art asfar as myknowledge of it extends, what I claim as my invention, and desire to secure by Letters Patent, 1s- 1. The process of toughening articles of 1o steel, consisting in, first, heating the article in a suitable furnace to a temperature showing a low orange color in the dark; secondly, rapidlyT cooling it to a temperature showing a clear red color in the dark by means of freelycirculating air, andfinally sealing it up in a 15 hot furnace and slowly cooling it.

The process of toughening articles of steel, consisting in heating them to a loT orange color, then subjecting them to a cooling action of air-currents, and then slowly zo cooling them in a sealed furnace.

In testimony WhereofI affix my signature in presence of two Witnesses.

JOHN COFFIN. Vtitnesses: r

J AMES CRANsToN, FRED W. STAMMLER. 

